Rheostat



April 10, 1956 E. F. MEKELBURG 2,741,685

RHEOSTAT Filed July 5, 1952 INVENTOR. 127/ z M2621 BY Q V United States PatentO RHEOSTAT Earl F. Mekelburg, Wauwatosa, Wis., assignor to Square D Company, Detroit, Mich., a corporation of Michigall Application July 5, 1952, Serial No. 297,347

7 Claims. (Cl. 201-62) This invention relates in general to rheostates; more particularly this invention relates to a rheostat of novel construction which may employ a plurality of types of current limiting elements.

One object of the present invention is to provide an improved rheostat which is economical to construct and maintain.

Another object of the present invention is the provision of a rheostat of new and improved form in which the current limiting elements may be readily changed.

Another object of the present invention is the provision of a new and improved rheostat having a plurality of paths therethrough for the passage of current.

Another object is the provision of a novel rheostat in which the amount of movement required of the element effecting the insertion of varying amounts of resistance in the electrical circuit is minimized.

Another object of the present invention is the provision of a rheostat having a rectilinearly operating control member which carries no current. Another object is the provision of an improved rheostat in accordance with the preceding object in which lateral force on the operating member is substantially minimized.

Another object of the present invention is the provision of a new and improved rheostat having a rectilinearly operable control member for varying the efifective resistance of the device, the new rheostat employing no flexible leads or pig tails whatsoever.

Another object of the present invention is the provision -.of'a new'and improved rheostat which may employ ribbon resistors, wire wound resistors, or similar current limiting elements with equal facility.

Other objects and features of the invention will be readily apparent to those skilled in the art from the specification and appended drawing illustrating certain preferred embodiments in which:

Figure l is a front elevational view of the device of :the present invention.

Figure 2 is an enlarged sectional view on the plane of .line lI-Il of Figure 1.

Figure 3 is a partial sectional view along the plane of line III-HI of Figure 2.

The device of the present invention comprises an enclosing case 1 comprising a base 2 having outer brackets '3 mounted thereto, as by welding, the brackets 3 serving to mount a cover 4. Screws 5 are provided which maintain the cover 4 in position as illustrated in Figure 2. To 'the inner surface of base 2 there are mounted a plurality of insulating plates 6 by means of bolts 7 and 8. Nuts '9 and 11 cooperate with bolts 7 and 8, respectively, to maintain plates 6 in position.

Spaced from the bolt 7 is a bolt 12, also projecting through the rear surface of the base 2, the bolt 12 being of conducting material and having its inner end mechanically and electrically connected to a conducting plate 13 by peening, welding or other suitable method. Extending through a suitable aperture in plate 13 is an elongated ice bolt 14, upon which there is mounted a plurality of conducting segments 15, 16, 17, 18, 19,21 and 22, these segments being separated from the bolt 14 by a suitable insulating sleeve 23.

As may be seen from an inspection of Figure 2, the segment 15 adjacent to plate 13 is electrically connected thereto, the opposite side of segment 15 being electrically connected to one end of a ribbon resistor 25, an insulating piece 24 being interposed between this end of the ribbon resistor25 and segment 16. The opposite end of resistor 25' engages the opposite face of segment 16 so as tobe electrically connected thereto, and is further electrically connected to one end of the adjacent ribbon resistor 26 which is insulated from the adjacent side of segment 17 by an insulating piece 27. As illustrated in Figure 2, other ribbon resistors 28 and 29, and a wire wound resistor 31, are provided and are assembled together with other insulating pieces 32, 33 and 34, and segments 18, 19, 21 and 22 in substantially the same manner as has previously been described for the assembly of the resistors 25 and 26. No insulating piece is interposed between segments 21 and 22. As will be seen from Figure 2, resistors 25, 26, 28, 29 and 31 and the insulating pieces 24, 27, 32, 33 and 34 are all positioned upon the bolt 14, the wire wound resistor being mounted thereto by end pieces 30.

Adjacent to, but spaced from, the bolt 8 is a conducting bolt 35 which extends through base 2 and is electrically and mechanically connected to the conducting plate 36 which is disposed at its interior end. A bolt 3'? extends through base 2 and a suitable hole in the plate 36 and supports, in the manner described in the paragraph immediately preceding, a plurality of resistance elements 38, 39, 41 and 42 which are of the ribbon type, and a single resistance element 43 of the wire wound type. In addition, there are mounted upon the bolt 37 conducting segments 50 through 56 comparable to and mounted as are the segments 15 through 19, 21 and 22 aforementioned. Insulating pieces 45 through 49 are provided and are interposed between the conducting segments 5% through 56 in the manner illustrated. An insulting sleeve 44 is provided which is similar to the insulating sleeve 23 aforementioned. ,For a reason to be substantially explained, the segments 50 and 15 are made of different size, while all of the other segments are of the same size, whereby the junctures between the segments of one stack are not aligned with junctures between the segments of the other stack.

An insulating plate 57 joins the ends of the bolts 14 and 37 and nuts 58 and 59 are disposed upon the ends of bolts 14 and 37 respectively. It will be obvious that all of the resistor elements may be of the ribbon type if desired, or all of the resistance elements may be of the wire wound type. it will further be obvious that any combination of these and other similar types of current limiting elements may be utilized, and that the number of segments and current limiting elements em ployed may be varied.

interposed between the bolts 14 and 37 and the stacks of segments which each carries is an operating shaft 61 which projects through suitable apertures in the base 2 and the cover 4. Riveted to the operating shaft 61 are a pair of laterally extending arms 62. Each of the arms 62 has an opening at each end in which there are disposed a spring 63 and a conducting brush 64, an insulating bar 7 65 being interposed between the biasing spring 63 and the brush 64. As will be seen from Figure 3, the spring 63 forces the brushes 64 into tight engagement with the conducting segments. The arms 52 are provided with projecting portions as which fit into the longitudinally extending openings in the springs 63 to maintain them in position. Springs 63 apply substantially equal and opsistorsi ifb, 42,41, 39 and 38'into segmentfithplate 3-6 v and.out. of the device thrpughgbolt 35.

if operating shaft 61 weremoved towardthel'eft, from thepositionof Figure 2, sothat the brushes-64 were carried "thereby toward the left, circuit current will flow through .fewe'r'resistance elements. Furthermore, it will be seen that dueto the relativeilateral displacement between the junctures of conducting segments in one row-and theijunctures of the conducting segments in'the other row, adequate area of contact between the brushes and the segments is always maintainedwhereby current carrying ability is not impaired. It will further be seen that when operating shaft 61 is moved into its most left position, fromthe view of Figure 2,,no resistance is in the electrical circuit of this, device, and that this no resistance position is :attained without an opening of the circuit whereby burning of brushes and segments when controlling inductive loads is eliminated.

It will readily beapparent that the device of the present invention .is readily'fabricated and that the contacting surfaces may be sanded or faced with ease. The conducting segmentsmayabe ofany suitable size, and may be inexpensive stampings. Furthermore, it is readily apparent thatvarious ;types of current limiting elements maybe employed, and that the deyiceutilizes movable operating. lever positionable, at will to smoothly vary the amount or resistance inthe. electrical circuit to-the device, but no flexible leads, .pig tails, or the like, need be employed. The operating lever of the present invention carries no current whatsoever and is isolated from the electrical circuits, while other elementsof the device present a plurality of paths for current flow through the struc- :ture.,

While certain preferredgembodiments of the invention have been specifically disclosed, it -is understoodthat the invention is notlimited thereto, as manywyariations will be readily'apparentto thoseskilled in the art and the invention isto be given -its broadeshpossibleinterpretation within the terms of the followingclaims.

.What is claimed ,is:

-1. Ina; device for regulatingcurrent flowv having a pair of terminals ,for connection to an electrical circuit, a plurality of conducting -segment s, a paircfspacedbolts supporting said segments inapairof spaced rows, insulating means disposed upon said bolts-betwen certain of said segments, other insulating meansdisposedbetween said bolts and said segments, firstimpedance means electrically interconnecting the segments of one of said rows, the ends of said first impedance means being mounted on one of said bolts, second impedance means electricallyinterconnecting the segments of the other of said 1'OWS,[h6 ends of said second impedance means beingmounted on the other of said bolts, one of said rows being electrically connected to one terminal while the other of said rows is electrically connected to the other of said terminals, 21 pair of movable conducting means, means mounting one of. said movable means in engagement with'one side of both of said rows of segments, means mounting 'the'other of said movable means in engagementwith the opposite side of both of said rows of segments, and means for moving said movable means along said rows to effect the insertion of'varlable portions of said impedance means in the electrical circuit between said terminals.

2 lna tilevice forregulatirig current flow having a pair of terminals for connection to an electrical circuina plurality of conducting segments, means supporting said segments in two rows,-insulating means separating said segments, first impedance means electrically interconnecting the segments of. oneof said rows, second impedance means electrically interconnecting the segments of the other of said rows, one ofsaid rows-being electrically con- 1 nected to one terminal while the other of said rows is electrically connected to theother of said "terminals, a pair of movable conducting means, an operating lever for rectilinearly moving said movable means, means mounting one ofsaid movable meansin engagement with one side of both of said rows and mounting the other of said movable means in engagement with the opposite side of both of said rows, said last mentioned means including one spring biasing said one movable means toward said rows and a second spring biasing said other movable means ftoward said rows, .said springsapplying substantially equal andropposite forceswhereby theresultanclateral force on said opearting leverzis minimized, said movable mea-ns being positionable by said operating lever along said rows to, efiectthe insertion of variable; portions of said impedance means in the electrical circuit between said terminals.

3. :In a device for regulating current flow havinga pair of terminals for connection to an electrical circuit, a plurality. of conducting segments,,a pair of spacedboltssupporting said segments in a pair of spaced rows, insulating means disposed upon said boltsbetweencertainofsaid segments, other insulating means disposed between said bolts and ,said segments, first impedance-means elect 'cally interconnecting thesegments of oneof said rows, th ends of said first impedance means being mounted-phone of said bolts, second impedance means electricallyinterconnecting the.segmentsoitheotherof saidmpws, the ends of said second impedance means-being ounted on theother-of said bolts, a pair of movable conducting means for-bridging said rows, an operating lever for rectilinearly moving-said movable means, means mounting one of said movable means in engagement with one side of both of said rows and mounting the other'of s aid movable means inengagement with-the oppositeside of both' .Qfsaid rows,. said last mentioned means including springs biasing said movable .means {toward said 1 rows, said springs applying substantially equal and opposite forces whereby the resultant lateral force on said operatg l ver i n ze ai m vabl mea -boneh ationable by said operating lever along said rows to ef fect the insertion of variable portions-of said impedancemeans in the electrical -circu;it between. said terminals.

I a de c r u tin c r n flQW-h v n ar of terminals for; connection to an electrical circuit, first bolt, a first stack of elements assembledthereon includsa pl a of fi s onduct se me m t 9 said first bolt, means insulating said-first segments from saidfirst b a p u a y o fi s 'in tia i spie e muta upon said first bolt, a plurality of first resistors of subt n i l U @hapem w 1 .12 i r s ab l ns device being so constructed and arranged that both ends of 1 id fir r si o ar moun e PPQ sai e s rb and disposed between; thetends. of; each first resistor; are at .least one of saidfirstsegmentaand at least one of said first insulating pieceswhereby no electricalcircuitbetween adjacent first segn ents erdsts .eggcept through said ,first resistors; removable means ggfor ti ghtly maintaining said first segments, fir st insulating .pieces and ,first. resistors ,in position ,upon lsaid'first'bolt; means electricallyconnecting said first stack of elements to one .ofisaid terminals; a second,boltrspaced from said first bolt,..a.second stack of elements assembled upon saidsecond bolt including a plurality of second conducting segments mounted upon said'secondbolt, means insulating said second segments from said second bolt, a plurality of second: insulating pieces mounted upon said second'bolt, a *plurality'bf second resistors of substantially U shape mounted upon said second bolt, said device being so constructed and arranged that both ends of said second resistors are mounted upon said second bolt and disposed between the ends of each second resistors are at least one of said second segments and at least one of said second insulating pieces whereby no electrical circuit between adjacent second segments exists except through said second resistors; removable means for tightly maintaining said second segments, second insulating pieces and second resistors in position upon said second bolt; means electrically conmeeting said second stack of elements to the other of said terminals; a pair of movable conducting means, means mounting one of said pair of movable conducting means in engagement with one side of both of said stacks and mounting the other of said pair of movable conducting means in engagement with the opposite side of both of said stacks, and a rectilinearly movable operating lever connected to said last mentioned means and movable to adjustably position said movable conducting means to effect the insertion of variable portions of said resistors in the electrical circuit between said terminals.

5. The device defined in claim 4 in which said means mounting said movable conducting means includes an insulating bracket which positions both of said movable conducting means in substantially the same plane.

6. The device defined in claim 4 in which said means mounting said movable conducting means includes an insulating bracket which positions both of said movable conducting means in substantially the same plane, and which also includes a spring associated with each of said movable conducting means acting to bias said movable conducting means toward said stacks.

77 The device defined in claim 6 in which said springs are so constructed and arranged that they apply substantially equal and opposed biasing forces whereby the resulting lateral thrust on said operating lever is minimized.

References Cited in the file of this patent UNITED STATES PATENTS 1,225,227 Dunham May 8, i917 FOREIGN PATENTS 860,970 France Oct. 15, 1940 

